Increased use of portable electronics such as cellular telephones, laptop computers and PDA's over the last several years has increased the demand for compact, low cost, and environmentally friendly rechargeable batteries.
Lithium based Solid Polymer Electrolyte (SPE) batteries have emerged as a forerunner in this growing technology. SPE batteries offer the optimal combination of performance, design flexibility, and safety. SPE batteries use solid lithium based polymers as their electrolyte (in place of traditional liquid electrolyte) sandwiched between a lithium metal sheet and a metal oxide sheet. This laminate construction allows for the creation of batteries which are as thin as a credit card and which can be configured in many different shapes and sizes. The use of a polymer electrolyte is also much safer and more environmentally friendly than traditional battery technologies. Unlike liquid based lithium batteries that use very volatile metallic lithium as their electrolyte, solid polymer batteries use a solid polymer electrolyte that is non-volatile, non-flammable and virtually leakproof since the electrolyte is itself a solid.
Presently, the most attractive cathode (note: the cathode is the negative electrode, however, during recharging operation the polarity switches between the electrodes) materials for use in SPE batteries are Li-based metal oxides such as LiCoO2, LiNiO2, LiFeO2 and LiMn2O4. These compounds are in a class of compounds known as intercalation compounds which allow the insertion and removal of guest species (especially metal ions) into their crystalline lattice structures. The commercial success of using such compounds as cathode materials, however, hinges upon the discovery of processes that produce intercalation compounds with the required electrochemical performance properties in a reasonable time and at a reasonable cost.
Traditionally, Li-based intercalation compounds have been formed by a mixed oxide process, in which the oxides react at high temperatures to form the desired compound. Typical methods require mixing of solid oxides followed by a high temperature calcination (heating) process in the temperature range of 600-1000° C. Many of these processes also require long heating times in the range of 5 hours to several days and multiple heating and/or grinding steps. (See, van Gehemen et al, U.S. Pat. Nos. 5,879,654 and 6,048,643, Sheargold et al, U.S. Pat. No. 5,702,679, Howard et al., U.S. Pat. No. 6,248,477) The long heating times and multiple grinding steps required by such processes drive up production costs considerably and introduce impurities. There is a need in the art of a synthesis process for Li-based intercalation powders which takes less time and is more cost effective than presently available methods.